body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #f0f0f0;
}

#gameCanvas {
    border: 1px solid #000;
}

body {
    flex-direction: column;
}
h1, p {
    text-align: center;
    width: 100%;
}

#gameCanvas, #startGame, #difficulty {
    margin: 10px 0;
}

#startGame, #difficulty {
    padding: 8px 16px;
    font-size: 16px;
}